The present invention relates to a circular knitting machine and in particular to the feeding of the thread to said machine to produce tubular knitwear such as socks and stockings, and relates to an impact protection device for a rod for positioning the feed threads at the active needle holders of a double cylinder machine.
Double cylinder circular knitting machines are generally essentially constituted by two coaxial rotating cylinders, each of which has a corresponding plurality of longitudinal grooves at its outer cylindrical surface.
Respective needles are guided in the grooves and form the loop of knitting in their vertical stroke by cooperating with the sinkers.
The number of grooves of the cylinders is equal to the number of the needles which run within them with a reciprocating vertical motion and are exchanged between the two cylinders: for the production of hosiery items in general, there can be up to 400 grooves per cylinder, whereas for the production of men's socks the number of needles is generally between 84 and 280.
The needles are fed, in their reciprocating vertical motion, in fixed angular positions and at the most protruding levels of their strokes with respect to the cylinder on which they are located, by feeder stations which in each instance supply the needles with the feeding thread which must be knitted in the portion of knitting being formed, in that row of knitting and in that angular position: every time the feed is changed, the previously fed thread must be swapped with the thread that constitutes the new feed.
Each feeding thread is carried by a thread guide which picks up the thread from a reel: the various thread guides are placed either on mutually different levels and/or at mutually different radial distances so that the paths that they follow do not interfere and so that a thread guide can carry its thread to knit without preventing another thread guide from removing its thread from the knitting.
In thread guide actuation devices, which are often of the rod-and-crank type, the end of the thread guide usually follows a specific path, usually a curved one, lying on a plane and is always equal so as to take it from an inactive position A to a position B in which the thread is placed next to the cylinder and vice versa.
The thread guides, together with the respective rods with which they are associated, are relatively bulky and very close to each other; accordingly, it often happens that as a thread guide approaches the cylinders it strikes or scrapes against a thread guide that has not yet moved away completely: this can lead to malfunctioning, jamming, or breakage of mechanical components or of the knitting threads.